This proposal focuses on the use of a specific secreted protein (SVS IV) of the rat seminal vesicle as a marker protein for the analysis of the mechanism of action of androgenic steroids. We plan to purify the messenger RNA for this protein and to synthesize a radioactively labeled complementary DNA molecule from it by use of Avian Myeloblastosis Virus reverse transcriptase. With the availability of the cDNA probe, we will carry out studies to determine whether the synthesis of SVS IV is regulated primarily at the transcriptional level under both in vivo and in vitro conditions. SVS IV is made in a cell-free protein synthesizing system in a precursor form, and we will determine the amino-terminal amino acid sequence of both the secreted, mature form of the protein and the form obtained by cell-free translation of its messenger RNA. We propose to isolate a recombinant DNA in the form of a derivative of bacteriophage lambda that has incorporated the entire gene region for SVS IV. Amplification of this viral vector will permit a start to be made on the nucleotide sequence of particularly interesting regions of the SVS IV gene region, for example, those abutting the 5' terminus of the SVS IV messenger. Principal techniques involve use of radioisotopes, immunological isolation of specific proteins, purification of mRNA by affinity chromatography and preparative electrophoresis, DNA-RNA hybridization, and use of restriction nucleases.